Abstract
Structural geological field work, microscopic and magnetic fabric studies have been applied in order to assess the structural origin of a gneiss dome, based on a regional example from the Neoproterozoic Pan-African Belt of NE Africa, the Wadi Hafafit Culmination (WHC). The culmination is dominated by a number of major shear zones, which form both the boundaries between the gneissic core and surrounding low grade successions as well as those of minor structural units within the gneisses. These shear zones form a linked fault system, which, based on shear criteria, fault-bend fold and overall geometric interrelationships, can be classified as an antiformal stack. The relative age sequence of the shear zones/thrusts with the highest thrust oldest and the lowermost youngest points to a forward-propagating thrust system. This, together with the shear criteria, exclude an origin of the WHC as a metamorphic core complex, where the highest shear zone should be youngest. The geometry of the WHC antiformal stack is documented by maps and sections as well as section balancing and restoration. Microscopic work showed brittle deformation in feldspar and dynamic recrystallization in quartz ribbons. The asymmetry of the fabric confirmed the macroscopically determined shear sense. However, there is one example of an earlier, perhaps extensional shear movement. Mylonitic foliation and transport-parallel lineation have also been determined by magnetic fabric studies. The observations suggest that thrusts may cut across both previously folded crystalline rocks as well as homogeneous granitoid plutonic bodies. According to the regional tectonic picture the large-scale structure of the gneiss dome originated after a phase of (late-orogenic) extensional collapse. It is speculated that during late-orogenic cooling the upper part of the lithosphere was sufficiently strong to allow brittle thrusting whilst the lithosphere as a whole was still weak enough to allow large-scale compressional deformation, perhaps in a transitional stage from lateorogenic to intra-cratonic deformation.
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References
Akaad M K and El Ramly M F 1963 Geology and structure of the Umm Lassaf-Umm Nar iron belt (Eastern Desert of Egypt);Geol. Surv. Mineral Res. Dept. Paper17 1–23
Bennett J D and Mosley P N 1987 Tiered-tectonics and evolution Eastern Desert and Sinai Egypt; InCurrent Research in African Earth Sciences (eds) G Matheis and Schandelmeier H (Rotterdam: Balkema) 79–82
Dahlen F A 1990 Critical taper model of fold- and-thrust belts and accretionary wedges;Ann. Rev. Earth Planet. Sci. 18 55–99
Dahlstrom C D A 1969 Balanced cross sections;Canadian J. Earth Sci. 6 743–757
Dewey J F 1988 Extensional collapse of orogens;Tectonics 7 1123–1139
El Akhal H 1993 A transect from a tectonic mélange to an island-arc in the Pan-African of SE Egypt (Wadi Ghadir Area);Scient. Ser. Int. Bureau 20 Forschungszentrum Jülich
El-Bayoumi R M A and Greiling R O 1984 Tectonic evolution of a Pan-African plate margin in South Eastern Egypt-A suture zone overprinted by low angle thrusting?; InAfrican Geology (eds) J Klerkx and J Michot, Musé royal de l’Afrique central, Tervuren 47–56
El-Gaby S and Greiling R O (eds) 1988The Pan-African belt of Northeast-Africa and adjacent areas. Vieweg, Braunschweig
El Gaby S, List F K and Tehrani R 1988 Geology Evolution and metallogenesis of the Pan African belt in Egypt; InThe Pan-African belt of northeast Africa and adjacent areas (eds) S El Gaby and R O Greiling, Vieweg, Braunschweig 17–68
El Kaliuobi B A and El Ramly M F 1991 Nomenclature origin and tectonic setup of the granite suite at Wadi Shait, SE Desert, Egypt;Annals Geol. Surv. Egypt 17 1–17
El-Ramly M F, Greiling R, Kröner A and Rashwan A A 1984 On the tectonic evolution of the Wadi Hafafit area and environs Eastern Desert of Egypt;Bull. Faculty Earth Sci. King Abdulaziz Univ.6 113–126
El Ramly M F, Greiling R O, Rashwan A A and Rasmy A H 1993 Explanatory note to accompany the geological and structural maps of Wadi Hafafit Area, Eastern Desert of Egypt;Geol. Surv. Egypt, Paper68 1–53
Eskola P 1949 The problem of mantled gneiss domesQ. J. Geol. Soc. London 104 461–476
Greiling R O and El Ramly M F 1990Wadi Hafafit area. Map, structural geology 1:100.000 TFH, Berlin
Greiling R O and Rashwan A A 1994 Large-scale shear-zones and related mineral deposits-examples from the Nubian Shield (Proterozoic, Egypt);Africa Geosci. Rev. 1 503–514
Greiling R O, Kröner A and El Ramly M F 1984 Structural interference patterns and their origin in the Pan-African basement of the southeastern Desert of Egypt; InPrecambrian Tectonics Illustrated (eds) A Kröner and R Greiling Schweizerbart’sche Verlagsbuchhandlung, Stuttgart 401–412
Greiling R O, Kröner A, El Ramly M F and Rashwan A A 1988 Structural and geological relationships between the southern and central parts of the Eastern Desert of Egypt; InThe Pan-African Belt of NE Africa and Adjacent Areas (eds) S El Gaby and R O Greiling, Vieweg, Braunschweig 121–145
Greiling R O, Gayer R A, Rice A H N, El Ramly M F and Rashwan A A 1990 Thrust tectonics in the Pan-African of Egypt: A model for a regional sole thrust;Centre Int. Form. Eck Geol. Publ. Occ. 1990/20 261
Greiling R O, Abdeen M M, Dardir A A, El Akhal H, El Ramly M F, Kamal El Din G M, Osman A F, Rashwan A A, Rice A H N and Sadek M F 1994 A structural synthesis of the Proterozoic Arabian-Nubian Shield in Egypt;Geol. Rundschau 83 484–501
Grothaus B, Eppler D and Ehrlich R 1979 Depositional environment and structural implication of the Hammamat Formation, Egypt;Annals Geol. Surv. Egypt 9 564–590
Hanmer S and Passchier C W 1991 Shear sense indicators: A review;Geol. Surv. Canada, Paper90–17 1–72
Hatcher R D and Hooper R J 1992 Evolution of crystalline thrust sheets in the internal parts of mountain chains; InThrust Tectonics (ed) K R McClay (London: Chapman & Hall) 217–233
Jelinek V 1981 Characterization of the magnetic fabric of rocks;Tectonophysics 79 63–67
Knipe R J 1990 Microstructural analysis and tectonic evolution in thrust systems: examples from the Assynt region of the Moine Thrust Zone, Scotland; InDeformation Processes in Minerals, Ceramics and Rocks (eds) D J Barber and P G Meredith (London: Unwin Hyman) 228–261
Kröner A and Greiling R (eds) 1984Precambrian tectonics illustrated; Schweizerbartsche Verlagsbuchhandlung, Stuttgart
Kröner A, Greiling R, Reischmann T, HusScin I M, Stern R J, Krüger J, Dürr S and Zimmer M 1987 Pan-African crustal evolution in the Nubian segment of Northeast Africa;Am. Geophys. Union, Geodyn. Series 17 235–257
Kröner A, Reischmann T, Wust H-J and Rashwan A A 1988 Is there any pre-Pan-African Basement in the Eastern Desert of Egypt?; InThe Pan African Belt of NE Africa and Adjacent areas (eds) S El Gaby and R O Greiling, Vieweg, Braunschweig 95–119
Kröner A, Todt W, HusScin I M, Mansour M and Rashwan A A 1992 Dating of late Proterozoic ophiolites in Egypt and the Sudan using the single grain zircon evaporation technique;Precambrian Res. 59 15–32
Lister G S and Davis G S 1989 Models for the formation of metamorphic core complexes and mylonitic detachment terranes;J. Structural Geol. 11 65–94
McClay K R (ed) 1992Thrust Tectonics (London: Chapman and Hall)
Munier R and Talbot C J 1993 Segmentation fragmentation and jostling of cratonic basement in and near Äspö, Southeast Sweden;Tectonics 12 713–727
Passchier C W and Trouw R A W 1996Microtectonics (Berlin: Springer-Verlag)
Passchier C W, Myers J S and Kroner A 1990Field geology of high-grade gneiss terrains (Berlin: Springer-Verlag)
Ramberg H1981 The Role of Gravity in Orogenic Belts;Geol. Soc. London Spec. Publ. 9 125–140
Ramsay J G 1967Folding and fracturing of rocks (New York: McGraw-Hill)
Rashwan A A 1991 Petrography Geochemistry and Petrogenesis of the Migif-Hafafit Gneisses at Hafafit Mine area Egypt;Scient. Ser. Int. Bureau 5 Forschungszentrum, Jülich
Reynolds S J and Lister G S 1990 Folding of mylonitic zones in Cordilleran metamorphic core complexes: Evidence from near the mylonitic front;Geology 18 216–219
Rice A H N, Greiling R O, Dardir A A, Rashwan A A and Sadek M F 1992 Pan-African extensional structures in the area south of the Hafafit Antiform Eastern Desert of Egypt:Zentralbl. Geol. Paläont. 1 1991 2641–2651
Rutter E H and Brodie K H 1992 Rheology of the lower crust; InContinental lower crust (eds) D M Fountain, R Arculus and R W Kay (Amsterdam: Elsevier) 201–267
Said R (ed) 1990The geology of Egypt; (Rotterdam: Balkema)
Schandelmeier H and Richter A 1991 Brittle shear deformation in Northern Kordofan Sudan: Late Carboniferous to Triassic reactivation of Precambrian fault systems;J. Structural Geol. 13 711–720
Schandelmeier H, Stern R J and Kröner A (eds) 1994 Geology of Northeast Africa;Geol. Rundschau 83 473–659
Simpson C and Schmid S M 1983 An evaluation of criteria to deduce the sense of movement in sheared rocks;Geol. Soc. Am. Bull. 94 1281–1288
Stern R J 1994 Arc assembly and continental collision in the Neoproterozoic East African Orogen;Ann. Rev. Earth Planet. Sci. 22 319–351
Stern R J and Hedge C E 1985 Geochronologic and isotopic constraints on Late Proterozoic crustal evolution in the Eastern Desert of Egypt;Am. J. Sci. 285 97–127
Takagi H 1989 Ductile shear zones: microstructures of mylonites InRheology of solids and of the Earth (eds) S Karato and M Toriumi (Oxford: Oxford Univ. Press) 338–350
Tarling D H and Hrouda F 1993The Magnetic Anisotropy of Rocks (London: Chapman and Hall)
Wernicke B 1995 Low-angle normal faults and Scismicity: a review;J. Geophys. Res. 100 20159–20174
Windley B F 1992 Proterozoic collisional and accretionary orogens; InProterozoic crustal evolution, (ed) K C Condie (Amsterdam: Elsevier) 419–446
Woodcock N H and Schubert C 1994 Continental strike-slip tectonics; InContinental deformation (ed) P L Hancock (Oxford: Pergamon Press) 251–263
Woodward N B Boyer S E and Suppe J 1989 Balanced Geological Cross-Sections: An Essential Technique in Geological Research and Exploration;Am. Geophys. Union Washington, DC
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Greiling, R.O. Thrust tectonics in crystalline domains: The origin of a gneiss dome. Proc. Indian Acad. Sci. (Earth Planet Sci.) 106, 209–220 (1997). https://doi.org/10.1007/BF02843448
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DOI: https://doi.org/10.1007/BF02843448